Elon Musk's roller coaster ride takes another turn

Five months ago, Elon Musk had about as great a week as anyone could imagine.

An unprecedented 276,000 people placed a down payment on his car company's new vehicle. Tesla's Model 3 was immediately poised to be one of America's best-selling cars when it's released in 2017. A tipping point for the electric car revolution appeared to have arrived.

A few days later Musk's rocket company, SpaceX, completed the dramatic landing of a rocket on a floating platform in the Atlantic Ocean. The feat was hailed as a huge step toward lowering the high costs of space flight.

Musk is obsessively pursuing space travel and electric cars because he believes they're essential to saving humanity. And he seemed well on his way to his lofty goals.

Yet for all the highs Musk's businesses have reached, there have also been low points and questions about the viability of his businesses. A new setback occurred on Thursday when a SpaceX rocket burst into flames on its Cape Canaveral launchpad.

The rocket, the Falcon 9, is the same one SpaceX has been expected to use to eventually transport NASA astronauts to the International Space Station.

The explosion, which Musk characterized as a "fast fire" on Twitter,occurred as SpaceX is in the middle of an aggressive launch schedule. Following a rocket explosion in June 2015, SpaceX did not make flights for six months and now haseven moreground to make up.

That's not the only issue for Musk's businesses. Tesla has missed its sales targets twice this year. The company will also now have to rapidly expand its manufacturing to meet the demand for nearly 400,000 Model 3s.

Ultimately, these challenges don't compare to the depths Musk's companies have recovered from in previous years.

In late 2008, both SpaceX and Tesla(TSLA) nearly went bankrupt, putting tremendous strain on Musk.

"I remember thinking this guy would have a heart attack and die," Talulah Riley, Musk's second wife, recalled in author Ashlee Vance's biography of the entrepreneur. "He seemed like a man on the brink."

With his own money, loans from friends and a timely NASA contract, Musk kept his businesses alive.

"Elon has 'bet it all' on a number of occasions," said Peter Diamandis, the founder of the X-Prize foundation and a friend of Musk's. "He stands alone both in terms of level of ambition and level of success."

In 2013, hard times forced Musk to set up a deal to sell Tesla to Google. But he backed away after his company's fortunes took a turn for the better.

While Tesla is currently burning through money as it builds out a Gigafactory to delivery batteries for the Model 3, funding is less of an issue. In May, Tesla raised $1.46 billion to finance the Model 3. It plans to raise more money later this year.

The company's stock price has outperformed the financial markets the last four years.

"Elon's companies are past their previous existential threats and are now about getting into the phase of matching his vision of the future," Diamandis said.

In July, Musk released an ambitious update to Tesla's master plan, which envisioned fleets of self-driving Teslas, electric trucks and tiny buses.

There's one other thing he's interested in building, according to Vance's biography of the entrepreneur. Rather than the cliche Silicon Valley perks such as free food and ping pong tables, Musk has considered installing a roller coaster on the Tesla and SpaceX campuses.

It would be a fun way to get around his buildings -- and also fitting for companies with no shortage of ups and downs.